On June 30 two men drove a dark green Jeep Cherokee into a set of doors at the Glasgow airport in Scotland, producing a burst of flames that officials deemed an act of terrorism. They linked the crash to a broader plot that included two cars in London that contained explosive materials.

The foiled plan is just one of the tens of thousands of terrorist pursuits that have pockmarked the globe in recent decades--including the 1972 murder of 11 Israeli athletes at the Munich Olympics, the 1975 hostage taking at the OPEC headquarters in Vienna, the 1995 sarin gas attacks in Tokyo, and the September 11, 2001, strikes in the U.S. Although terrorism includes a diversity of actions, all of them, by definition, are intended to harm innocent civilians--and perpetrate fear--in the name of political, religious or other ideological goals.